Fig.1: The Receiver
GSM
Mechanical
Switch
External RF
V_G_LNA
FL303
FL302
FL301
FL300
27
29
26
13
V_P_LNA
PCN
Diplexer
L305
PCN RX =1805-1880Mhz
GSM RX = 935-960Mhz
17
LNA
LNA
LNA
20 21
FL304
To IF Amp
8 9
RX_ON2
15
PMB2410
(IC300)
RX UHF VCO
GSM UHF VCO = 1205 – 1230Mhz
PCN UHF VCO
1535 – 1610Mhz
270Mhz
The rf signals from L305 form the inputs to the active double-balanced rf mixer of
IC300 #13-#14. These are mixed with the UHF VCO (GSM 1205Mhz-1230Mhz,
PCN 1535Mhz -1610Mhz) which is input to IC300 #17-18. When these two rf
signals are mixed a resultant signal of 270Mhz is produced, this is the
intermediate frequency (IF). The signal RX_ON2 (derived from IC27-#28) is the
control input which enables the mixer. Outputs from the mixer are differential with
the signals phase shifted by + and - 90 degrees. These are then fed into a Dual IF
SAW filter (FL304) and then back into IC300 #8-#9.
The RX IF of 270Mhz has been selected based on the number of image response
and intermodulation products in the IF band, subject also to the constraints that
harmonics of the IF do not fall within any RX and TX band and harmonics of the
13Mhz TCXO do not fall in the IF band.
The differential IF signal is then fed to the IF amplifier, within IC300 (see figure.3:
The IF Amp and demodulator). The gain of the amplifier is controlled by the
Superchip – IC27, using 3 AGC Control lines:
SYGCDT
: AGC Programming Data Line (#75)
PGCSTR
: AGC Programming Enable Line (#72)
SYGCCL
: AGC Programming Clock Line (#74)
These signals are output from IC27 on the logic board. The IF amp can be
programmed to a range of 0dB to 70dB in 2dB steps, some 36 levels.
Summary of Contents for DB2000
Page 1: ...DB2000 Service Manual Help ...
Page 3: ... ...
Page 5: ... 2 3 4 2 2 2 2 2 0 0 0 5 3 4 2 6 2 7 2 2 2 2 0 8 9 2 2 2 2 2 2 2 2 ...
Page 7: ... 2 6 2 2 2 2 2 3 4 2 2 0 2 ...
Page 8: ... 2 ...
Page 9: ... Previous Section Next Section Main Menu Section 2 Unit Specifications ...
Page 77: ... 1 2 ...
Page 83: ...Fit Antenna INSERT AND SCREW THE ANTENNA INTO THE ASSEMBLY ...
Page 107: ...Fig 3 7 GSM_LNA Pg 3 3I TP419 Fig 3 8 PCN_LNA Pg 3 3J TP420 Fig 4 9 TCXO Pg 2 H11 TP413 ...
Page 109: ...Fig 4 3 PCN_TX Pg 1 1J TP417 Fig 4 4 3V_G_TX Pg 1 4I TP100 Fig 4 5 3V_P_TX Pg 1 4J TP101 ...
Page 110: ...Fig 4 6 GSM_ON Pg 1 2K TP402 Fig 4 7 PCN_ON Pg 1 1K TP415 Fig 4 8 PRE_ON Pg 1 4J TP416 ...
Page 112: ... I Q ...
Page 113: ...Fig 4 14 V_ERROR PCN Pwr Lvl 7Pg 1 16I Fig 4 15 300khz Charge Pump Pg 1 Log 9G ...
Page 115: ... Previous Section Next Section Main Menu Section 6 Device Device Information Information ...
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Page 190: ... Previous Section Next Section Main Menu Glossary of Terms ...